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SSD and HDD capacity goes on embiggening

But is it better?

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Capacity increase rates

The SanDisk/Sony Memory Stick PRO roadmap goes from 16GB maximum capacity to 32GB and then on to 2TB. If we assume a capacity increase rate of 50 per cent a year on average that gives us the following timetable:

Toshiba has announced a 500GB 2.5-inch HDD late last year, joining other suppliers such as Seagate. Lets have a start point of 500GB in 2009 and, applying a 50 per cent per annum capacity increase rate, see what we get:

2011 - 1TB
2013 - 2TB
2015 - 4TB
2017 - 8TB
2019 - 16TB
2021 - 32TB

We get parity, ignoring that slight difficulty of a TB being 1024GB in one table and 1000GB in the other. So let's say we get rough parity. That will make life interesting.

Of course this destination point is erected on an assumption of 50 per cent per year capacity increases with both SSD and HDD technology. That could be wrong. HDD suppliers, feeling the heat of SSD pursuit, could aim to raise capacity faster than this. The flash suppliers may run into technology difficulties. Who knows? We're guesstimating here.

Also there isn't one SSD capacity increase curve but several, one for each cell bit density level.

The picture is complicated by cost/GB differences between the two technologies and price decline rates as well as by I/O speed and write endurance differences. (If anyone can offer intelligence about the comparative price decline rates for HDDs and SSDs, that would be very interesting to know.)

One conclusion is that it is going to become harder to distinguish the right random-access storage technology to use in particular applications, choosing between, say, differently priced and capacity level 2.5-inch HDDs with SATA or SAS interfaces and 5,400rpm, 7,200rpm, and 10,000rpm spin speeds on the one hand, and differently priced and capacity level 1X, 2X, 3X, 4X and maybe even 5X 2.5-inch SSDs on the other, with various speeds and write endurance levels - not to mention hybrid devices with thumping great NAND caches in front of their spinning platters.